The present invention relates to a tube for suppressing radiation of undesired electromagnetic waves from an electric cable connected to a digital electronic device or the like.
As is well known, a digital electronic device comprises a number of electronic components, such as a random access memory (RAM), a read-only memory (ROM), a microprocessor, and others. Each of these electronic components comprises a number of logic elements, and these electronic components are mounted on a printed circuit board having signal lines (wired conductors) wired around thereon. In recent digital electronic devices, the operation speed of the logic elements can be increased and further the reduction in weight, thickness, length and size of the device has been rapidly advanced. Following this, the mounting density of the electronic components onto the printed circuit board has also been rapidly enhanced.
However, since a signal flowing in the logic element goes with abrupt changes in voltage and current, the electronic component is a generation source of high frequency noise. The high frequency noise causes interactions cooperatively with crosstalk noise or noise due to impedance mismatch so as to induce malfunctions relative to other electronic components in the printed circuit board and to adversely affect other systems. Further, following the high-density mounting of the electronic components onto the printed circuit board and the reduction in size of the electronic components, the electrostatic coupling between the electronic components is increased so that the electromagnetic interference is liable to occur in the digital electronic device.
The digital electronic device to be such a noise generation source is connected to other digital electronic devices and a power supply socket via cables.
Accordingly, it is possible that undesired electromagnetic waves are radiated from the cables. Since the undesired electromagnetic waves adversely affect the other electronic devices, it is necessary to suppress it. However, conventionally, no measures have been taken relative to the undesired electromagnetic waves radiated from the cables.
Therefore, an object of the present invention is to provide a composite magnetic tube and its producing method, and an electromagnetic interference suppressing tube which can be used for suppressing radiation of undesired electromagnetic waves from a cable connected to a digital electronic device or the like.
When a plurality of vinyl coated wires (cables) are wired, it is general to bundle them using a bundling band or spiral tube of synthetic resin. In this case, power lines and signal lines are often mixed. In case of the mixed wiring, electric signals are degraded due to increase and induction of crosstalk and, following this, it is possible that a circuit malfunctions.
Another object of the present invention is to provide a composite magnetic tube and its producing method, and an electromagnetic interference suppressing tube which can suppress mutual interferences even when a plurality of vinyl coated wires (cables) are bundled.
A further object of the present invention is to provide a bundling tube which can not only bundle a plurality of cables, but also suppress undesired radiant noise generated from the cables.
According to the present invention, as recited in claim 1, there is obtained a tube made of a composite magnetic material composed of an organic binding agent and soft magnetic powder mixed with and dispersed in the organic binding agent.
According to the present invention, as recited in claim 2, there is obtained a tube having a two-layered structure comprising an inner-side composite magnetic layer made of a composite magnetic material composed of an organic binding agent and soft magnetic powder mixed with and dispersed in the organic binding agent, and a conductor layer provided on an outer surface of the composite magnetic layer.
Modifications of these tubes or preferred examples of organic binding materials or soft magnetic materials to be used are recited in claims 3 to 10.
As recited in claim 13 or 14, the tube is suitable to be used as a cover tube for suppressing an undesired electromagnetic interference or as a bundling tube with respect to electric cables. For convenience of mounting onto the cable, it is preferable as recited in claim 11 or 12 that the tube is formed with a slit in a longitudinal direction or formed into a spiral structure.
According to the present invention, as recited in claim 15, there is obtained a method of producing a tube made of a composite magnetic body, characterized in that a melt of a composite magnetic material composed of soft magnetic powder mixed with and dispersed in an organic binding agent is extruded through a die so as to form an annular tube.
Further, as recited in claim 16, a tube with a slit can be obtained by forming the slit in the foregoing annular tube along a longitudinal direction thereof.
Further, as recited in claim 17, a tube of a spiral structure can be obtained by forming a spiral slit in the foregoing annular tube along a longitudinal direction thereof.